Chief Executive Bob Diamond and Chairman Marcus Agius are to be questioned later this week.

Barclays Chairman Marcus Agius on Monday stepped down over the Libor scandal. His resignation comes after the bank was fined £290 million for trying to tweak the Libor.

The bank confirmed his resignation in its latest announcement. In his resignation letter Agius said: "I am the ultimate guardian of the bank's reputation. Accordingly, the buck stops with me and I must acknowledge responsibility by standing aside."

Agius apologised to the bank's customers and employees for letting them down. "I am truly sorry that our customers, clients, employees and shareholders have been let down. Barclays is full of hard working, talented individuals whose integrity is not in question," Agius added.

Although the bank said Agius had no plans of quitting on Saturday, he did quit duly extending an apology.

Agius has been the chairman of Barclays since 2007 and is also the chairman of the British Bankers' Association (BBA). He will be expected to relinquish the BBA post also after stepping down from Barclays.

Pressure had been mounting on top bank officials as soon as the news emerged that some of the traders attempted to manipulate the setting of Libor. Libor has been used as a benchmark for setting rates worldwide.

Barclays also admitted last week that some of its traders tried to manipulate the setting.

In his resignation letter, Agius said the recent events "evidencing as they do unacceptable standards of behaviour within the bank - have dealt a devastating blow to Barclays reputation."

Barclays' Chief Executive Bob Diamond will be questioned by MPs about the scandal on Wednesday. Diamond will primarily be quizzed on his relationship with the Bank of England, but he may even reveal Barclays was not the only bank involved in such practices.

A hunt is on for a possible replacement for Agius. Board member Sir John Sunderland will be spearheading the search for the successor. Reports are already doing the rounds that Sir Mike Rake, the chairman of BT group, will be roped in for the job. Sir Mike Rake has been appointed as the Deputy Chairman, announced the Bank.

Critics want more heads to roll in the saga. "Marcus Agius going and Bob Diamond staying would be no solution to this scandal. Diamond is the driver and Agius the passenger in the Barclays car crash," said Lord Oakeshott of the Lib Dems, reports the Guardian.

The Financial Services Authority (FSA) may not want the exit of both the chairman and the chief executive of a major bank like Barclays at the same time, it is reported.

Agius' resignation is likely to have contagion effect as a probe is already under way into RBS, HSBC, UBS and Citigroup. Bigger fines are on the cards as a dozen other banks are under investigation.